Liquid crystal elastomer-liquid metal hollow fiber as well as preparation method and application thereof in artificial muscle bundle

Abstract

The invention discloses a liquid crystal elastomer-liquid metal hollow fiber and a preparation method and application in an artificial muscle bundle, the liquid crystal elastomer-liquid metal hollow fiber is of a three-layer-core bundle-shaped fiber structure, the material of the outermost layer is a liquid crystal elastomer of a dynamic covalent bond, dynamic bond exchange can occur under external stimulation, and the liquid crystal elastomer-liquid metal hollow fiber is a liquid crystal elastomer of a dynamic covalent bond. The material of the middle layer is a liquid crystal elastomer with thermal response, phase transformation occurs under the heating condition, so that macroscopic shrinkage deformation is caused, and the material of the core layer is flowing liquid metal and has electrical conductivity and electric heating performance. The artificial muscle bundle has good sensing performance, can sense mechanical changes such as pulling, bending, extruding and hanging heavy objects, and also can monitor changes such as external temperature; the artificial muscle bundle has excellent driving performance and has the advantages of being high in response speed, large in shrinkage rate, large in working capacity and the like.

Description

Technical Field

[0001] The invention relates to the technical field of intelligent materials, and in particular to a liquid crystal elastomer-liquid metal hollow fiber, a preparation method thereof, and an application thereof in an artificial muscle bundle. Background Art

[0002] Artificial muscle is a flexible actuator that can deform under the stimulation of external signals (light, electricity, heat, etc.). The main materials used to make artificial muscles are dielectric elastomers, shape memory alloys, nylon wires, graphene fibers, carbon nanotube fibers, etc. The development of artificial muscles has made great progress. They have gradually developed into having advantages such as high safety, high freedom of movement, strong adaptability and large contraction rate, but are limited to the driving functions such as contraction, bending and spiral. In recent years, the development of artificial muscles has begun to turn to artificial muscles with sensing functions. These artificial muscles can self-monitor the state of movement and use the output deformation signals for future human-computer interaction, providing an effective method to meet the requirements of agile movement and rapid response of the human body interacting with them. These artificial muscles with sensing functions are usually prepared by two methods. One is to use strain or pressure sensors to monitor the contractile artificial muscles in real time, but at the same time, some inevitable problems will be encountered, such as the deformation and connection mismatch between the driving materials and sensor components of the artificial muscles, resulting in inaccurate deformation monitoring and component failure. Another method is to combine conductive functional materials such as graphene oxide, carbon nanotubes, MXene, silver nanowires, etc. with driving materials to form artificial muscles with sensing functions.

[0003] Although some progress has been made in artificial muscles with sensing functions, the following problems still exist: first, it is difficult to simultaneously obtain high sensitivity and large drive deformation; second, many artificial muscles with sensing functions integrate sensing and drive functions into the same fiber or device, so partial damage to a single fiber will lead to failure of the overall function; third, when a single fiber is used as the only carrier pathway for energy input and signal output, it may cause mutual interference between the two, thus causing deviations in the output sensor signal. Moreover, the existing preparation methods and processes for artificial muscles with sensing functions are relatively complex and are not suitable for large-scale mass production. Summary of the invention

[0004] The purpose of the present invention is to provide a liquid crystal elastomer-liquid metal hollow fiber in view of the technical defects existing in the prior art. Among them, liquid crystal elastomer (LCE), as a new type of intelligent material, has both the elasticity of elastomer materials and the fluidity and orderliness of liquid crystal materials, and is a bidirectional shape memory material. When stimulated by external conditions, the liquid crystal primitives change from the anisotropic phase of uniaxial arrangement to the isotropic phase of disordered arrangement, resulting in reversible macroscopic deformation of the material, making it have a wide range of application value in the fields of soft actuators and the like. Liquid metal (LM) is an amorphous, flowable liquid metal material that has the properties of both fluids and metal conductors, and has many advantages such as high conductivity, thermal conductivity, good biocompatibility and unlimited deformation ability. It can be added to polymer materials as a new type of functional fluid filler to form liquid metal polymer materials, which are widely used in the fields of soft actuators, artificial muscles, smart wearable devices, etc.

[0005] Another object of the present invention is to provide a method for preparing the liquid crystal elastomer-liquid metal hollow fiber. The liquid crystal elastomer hollow fiber with dynamic chemical bonds on the surface is prepared by a centrifugal rotation method, and liquid metal is further injected into the interior of the hollow fiber to form a "skin-core structure" of the liquid crystal elastomer-liquid metal hollow fiber.

[0006] Another object of the present invention is to provide an application of the liquid crystal elastomer-liquid metal hollow fiber in an artificial muscle bundle. By heating, the dynamic covalent bond recombination is triggered, so that multiple "skin-core structure" artificial muscles form an artificial muscle bundle that integrates perception and drive.

[0007] The technical solution adopted to achieve the purpose of the present invention is:

[0008] A liquid crystal elastomer-liquid metal hollow fiber, which is a bundle fiber structure with a three-layer core. The material of the outermost layer is a liquid crystal elastomer with dynamic covalent bonds, which can undergo dynamic bond exchange under external stimuli (such as light, heat, electric heat or humidity). The material of the middle layer is a thermally responsive liquid crystal elastomer, which can undergo phase transition when heated, thereby causing macroscopic shrinkage deformation. The core layer material is a flowing liquid metal with electrical conductivity and electrothermal properties.

[0009] In the above technical solution, the thickness of the outermost layer ranges from 3μm to 1000μm, the thickness of the middle layer ranges from 3μm to 1000μm, the diameter of the core layer material ranges from 2μm to 1200μm, and the length of the bundled fibers ranges from 15mm to 1500mm.

[0010] In the above technical solution, the dynamic covalent bond is an ester-based dynamic bond, a disulfide-based dynamic bond, a boron-oxygen-based dynamic bond, a silicon ester-based dynamic bond, a diselenide-based dynamic bond, or a nitrogen-containing functional group-based dynamic bond;

[0011] (1) Dynamic bond exchange reaction based on esters

[0012]

[0013] (2) Dynamic bond exchange reaction based on disulfide bonds

[0014]

[0015] (3) Dynamic bond exchange based on boron-oxygen bonds

[0016]

[0017] (4) Dynamic bond exchange based on silicone ester

[0018]

[0019] (5) Dynamic bond exchange based on diselenium

[0020]

[0021] (6) Dynamic bond exchange based on nitrogen-containing functional groups

[0022]

[0023]

[0024] (7) Others

[0025]

[0026] The liquid crystal monomer with a single functional group used in the material of the outermost layer is one or more of the following:

[0027]

[0028] Wherein, n=2~13, m=1~12, X=H、Cl、F、CH 3。 ;

[0029] The dual monofunctional liquid crystal monomers used in the outermost layer of the material are one or more of the following:

[0030]

[0031] Wherein, n=2~13, m=1~12, X=H、Cl、F、CH 3。 ;

[0032] In the above technical solution, the dynamic covalent bond monomer in the outermost layer of the material includes one of the following (1) to () (1)

[0034] (2)

[0036] (3)

[0038] (4)

[0040] (5)

[0042] (6)

[0044] (7)

[0046] (8)

[0048] (9)

[0050] (10)

[0052] (11)

[0054] (12)

[0056] (13)

[0058] (14)

[0060] (15)

[0062] (16)

[0064] (17)

[0066] (18)

[0068] (19)

[0070]

[0071] In the above technical solution, the liquid crystal used as the material of the intermediate layer is a polymerizable liquid crystal monomer with different reactive functionalities at the end, and the liquid crystal phase transition temperature of the liquid crystal monomer is 25° C. to 180° C. Preferably, the liquid crystal monomer is a single liquid crystal monomer or a mixture of two or more liquid crystal monomers. More preferably, the monofunctional liquid crystal monomer is one or more of the following:

[0072]

[0073] Wherein, n=2~13, m=1~12, X=H、Cl、F、CH 3。 ;

[0074] The dual monofunctional liquid crystal monomer is one or more of the following:

[0075]

[0076] Wherein, n=2~13, m=1~12, X=H、Cl、F、CH 3。 .

[0077] In the above technical solution, the liquid metal is composed of the following components and mass percentages: 52-78% gallium, 5-12% indium, 0.5-2% copper, 7-20% zinc, 0-1.2% aluminum, and 0-18% tin. The phase transition temperature of the liquid metal is 0-35°C, and it can stably maintain liquid state in a low temperature environment, and has excellent fluidity and conductivity, ensuring that the liquid crystal elastomer-liquid metal hollow fiber can maintain and work normally at both low and high ambient temperatures.

[0078] Another aspect of the present invention also includes a method for preparing the liquid crystal elastomer-liquid metal hollow fiber, comprising the following steps:

[0079] Step 1, cleaning the tubular mold and then drying it;

[0080] Step 2, injecting the mixed stock solution with dynamic covalent bonds into the mold, standing for a period of time to react, fixing it on a high-speed motor for high-speed rotation, the motor rotation speed is 500-5000rpm, forming a layer of liquid crystal hollow film with dynamic covalent bonds on the inner wall of the mold, preferably, in order to increase the thickness of the liquid crystal hollow film, it can be repeatedly spin-coated; further using a polymerizable liquid crystal monomer stock solution with different reaction functionalities at the end for spin coating, standing for a period of time to react, forming a hollow cortical structure with an outer layer of a liquid crystal elastomer layer with dynamic covalent bonds and a middle layer of a thermally responsive liquid crystal elastomer layer;

[0081] Step 3, immersing the mold treated in step 2 in hydrofluoric acid for etching, repeatedly washing the liquid crystal layer of the mold with clean water, drying it, and then stretching it to change it from a multi-domain state to a single-domain state, stretching it to 150% to 200% of its original length, and further irradiating it with ultraviolet light to cross-link the carbon-carbon double bonds inside the fiber to obtain a hollow liquid crystal hollow tube with an outermost layer and an intermediate layer;

[0082] Step 4: injecting liquid metal into the hollow liquid crystal hollow tube to form the liquid crystal elastomer-liquid metal hollow fiber.

[0083] In the above technical solution, in step 4, glue is used to seal both ends and the ends are connected to metal wires. Preferably, the viscosity of the glue ranges from 300 to 10,000 cps, and the glue is modified acrylic adhesive, epoxy resin glue, polyvinyl acetal glue, α-ethyl cyanoacrylate, etc.

[0084] In the above technical solution, the mold in step 1 is a glass capillary, which is ultrasonically cleaned in ethanol and deionized water during cleaning. Preferably, the length of the glass capillary ranges from 10 mm to 1000 mm, and the inner wall diameter of the glass tube ranges from 10 μm to 2000 μm.

[0085] In the above technical solution, in step 2, the mixed stock solution with dynamic covalent bonds includes dynamic covalent bond monomers, liquid crystal monomers with monofunctional groups, liquid crystal monomers with dual monofunctionality, chain extenders, crosslinkers and photoinitiators, wherein the content of the monomers with dynamic covalent bonds is 5% to 25%, the content of the liquid crystal monomers with monofunctional groups is 0% to 40%, the content of the liquid crystal monomers with dual monofunctionality is 50% to 90%, the content of the chain extender is 20% to 40%, the content of the crosslinker is 30% to 50%, and the content of the photoinitiator is 0.5% to 2%;

[0086] The polymerizable liquid crystal monomer stock solution with different reactive functionalities at the ends includes a liquid crystal monomer with a monofunctional group, a liquid crystal monomer with dual monofunctionality, a chain extender, a crosslinking agent and a photoinitiator, wherein the content of the polymerizable liquid crystal monomer with a monofunctionality is 0% to 45%, the content of the polymerizable liquid crystal monomer with dual reactive functionality is 60% to 95%, the content of the chain extender is 15% to 45%, the content of the crosslinking agent is 25% to 55%, and the content of the photoinitiator is 0.5% to 2%.

[0087] In the above technical solution, the concentration of hydrofluoric acid used in step 3 is 5% to 40%, the etching time is 10min to 50min, the wavelength of the ultraviolet lamp used is 365nm, and the light intensity is 10 to 300mW / cm 2 , the illumination time is 2 to 30 minutes.

[0088] Another aspect of the present invention also includes the use of the liquid crystal elastomer-liquid metal hollow fiber in an artificial muscle bundle, wherein the artificial muscle bundle is formed by two or more liquid crystal elastomer-liquid metal hollow fibers through dynamic covalent bond exchange on the surface of the fiber bundle.

[0089] In the above technical solution, two or more liquid crystal elastomer-liquid metal hollow fibers are placed side by side and closely attached to each other, and then bonded together by heating. The heating temperature is 40 to 100° C. and the heating time is 10 to 100 minutes.

[0090] Compared with the prior art, the present invention has the following beneficial effects:

[0091] 1. The liquid crystal elastomer-liquid metal hollow fiber with a "skin-core structure" prepared by a rotation method in the present invention has convenient tube diameter and length control, uniform skin structure of the outermost layer and the middle layer, and adjustable skin thickness. The skin material can be prepared from one or more materials, which provides the possibility for the functionalization of the fiber.

[0092] 2. The liquid crystal elastomer-liquid metal hollow fiber prepared by the present invention can monitor mechanical sensing such as stretching, bending, extrusion, twisting and hanging heavy objects, and can also monitor temperature changes, etc., and has good sensing sensitivity and mechanical properties.

[0093] 3. The liquid crystal elastomer-liquid metal hollow fiber of the present invention has good driving performance, with the fastest response time reaching 0.12s, the maximum contraction rate exceeding 98%, and the maximum working capacity of 78J / kg, which exceeds the performance of most artificial muscles.

[0094] 4. The fiber bundle in the liquid crystal elastomer-liquid metal hollow fiber prepared by the present invention has multiple independently controlled passages, which can independently monitor the contraction deformation state of the fiber in real time during the electric drive process, avoiding the interference between the driving and sensing performances. At the same time, by assembling multiple fibers together, the ability of the fiber to lift heavy objects can be further greatly improved.

[0095] 5. The artificial muscle bundle of the present invention has good sensing performance, and can sense mechanical changes such as pulling, bending, squeezing and hanging heavy objects, and can also monitor changes such as external temperature; the artificial muscle bundle also has excellent driving performance, and has the advantages of fast response speed, large contraction rate and large working capacity. These artificial muscles can be used in artificial arms and artificial fingers, can monitor deformation when lifting heavy objects, and can sense the shape of objects. BRIEF DESCRIPTION OF THE DRAWINGS

[0096] Figure 1 This is the preparation process of liquid crystal / liquid metal fiber.

[0097] Figure 2 This is the morphology of liquid crystal / liquid metal fiber.

[0098] Figure 3 Liquid crystal / liquid metal fiber sensing performance.

[0099] Figure 4 Driving performance for liquid crystal / liquid metal fibers.

[0100] Figure 5 Proprioceptive actuation sensing for liquid crystal / liquid metal artificial muscle fiber bundles.

[0101] Figure 6 Liquid crystal / liquid metal artificial muscle fiber bundles have the function of recognizing object shapes. DETAILED DESCRIPTION

[0102] The present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0103] Example 1 1.1

[0105] A liquid crystal elastomer-liquid metal hollow fiber is prepared by the following method: Figure 1 As shown:

[0106] Step 1, ultrasonically clean a glass capillary with a length of 50 mm and an inner diameter of 1000 μm in ethanol and deionized water, and then dry it;

[0107] Step 2, injecting the mixed stock solution with dynamic covalent bonds into the capillary wall, wherein the content of the monomer with dynamic covalent bonds is 9%, the content of the liquid crystal monomer with monofunctional groups is 10%, the content of the liquid crystal monomer with dual monofunctionality is 50%, the content of the chain extender is 20%, the content of the crosslinker is 10%, and the content of the photoinitiator is 1%. After standing for a period of time to react, it is fixed on a high-speed motor for high-speed rotation, and the motor rotates at a speed of 1000rpm. After repeated spin coating, a layer of liquid crystal hollow film with dynamic covalent bonds with a thickness of 30μm is formed on the capillary wall;

[0108] Further, a polymerizable liquid crystal monomer stock solution with different reactive functionalities at the end is repeatedly spin-coated, wherein the content of liquid crystal monomer with a single functional group is 35%, the content of liquid crystal monomer with dual single functionality is 35%, the content of chain extender is 20%, the content of cross-linker is 9%, and the content of photoinitiator is 1%. After standing for a period of time to react, it is fixed on a high-speed motor for high-speed rotation, and the motor rotates at a speed of 1500rpm. After repeated spin coating, a layer of liquid crystal hollow fiber with a thickness of 50μm is formed on the capillary wall;

[0109] Step 3, immersing the glass capillary in hydrofluoric acid for etching, repeatedly washing the liquid crystal layer of the etched glass tube with clean water and drying it, and then stretching it to change it from a multi-domain state to a single domain state, stretching it to 150% of its original length, and further irradiating it with ultraviolet light to cause the second step of cross-linking, the concentration of the hydrofluoric acid used is 40%, the etching time of the glass tube is 10 minutes, the wavelength of the ultraviolet light used is 365nm, and the light intensity is 300mW / cm 2 , the illumination time is 30min;

[0110] Step 4: Inject liquid metal into the hollow liquid crystal tube to form a liquid crystal / liquid metal fiber with a "skin-core structure", such as Figure 2 As shown, the gallium content in the liquid metal is 78%, the indium content is 12%, the copper content is 1%, the zinc content is 10%, the aluminum content is 1%, and the tin content is 8%; then a metal wire is connected to the end of the fiber, and α-ethyl cyanoacrylate is used to seal both ends.

[0111] The dynamic covalent bond used in the outermost material of this embodiment is an ester-based dynamic bond, and the dynamic covalent bond monomer structure contained in the outermost material is as follows:

[0112]

[0113] The structural formula of the monofunctional polymerizable liquid crystal monomers in the outermost layer and the middle layer of this embodiment is as follows:

[0114]

[0115] The structural formula of the bifunctional polymerizable liquid crystal monomers in the outermost layer and the middle layer of this embodiment is as follows:

[0116]

[0117] Furthermore, we tested the sensing performance of the liquid crystal / liquid metal fiber. In this embodiment, we prepared a liquid crystal / liquid metal fiber with a wall thickness of 50 μm, and tested the sensing signals output when the fiber was stretched, bent, and compressed. Figure 3 As shown, the experiment shows that as the thickness of the liquid crystal cortex in the middle layer of the fiber becomes thinner, the sensitivity of the fiber becomes higher. Therefore, the liquid crystal / liquid metal fiber with a wall thickness of 50μm has the highest sensing sensitivity, and under the three force mechanisms, compressing the cross-section of the fiber will cause the signal change to be very obvious. 1.2

[0119] A liquid crystal elastomer artificial muscle bundle with sensing function is prepared by the following method:

[0120] Two fibers are placed side by side and closely attached together, and then the fiber bundle is heated to trigger the bond exchange of dynamic covalent bonds, which can further assemble into an artificial muscle fiber bundle. Furthermore, the heating temperature is 50° C. and the heating time is 100 min.

[0121] When different electricity is applied, the fiber bundle has different shrinkage speeds and shrinkage rates, such as Figure 4 As shown in the experiment, the contraction speed and contraction rate increase with the increase of the voltage. Furthermore, the fiber bundle is assembled on an artificial arm. When electricity is applied, the fiber bundle can contract and pull the artificial arm up. At this time, the contraction process of the fiber bundle is recorded by the sensor fiber in the fiber bundle, realizing real-time signal feedback, such as Figure 5 At the same time, the fiber bundle can be further assembled into an artificial finger. When powered on, the finger can be bent and pressure can be formed between the finger and the object. By sliding the object, the shape of the object surface can be fed back in real time, such as Figure 6 shown.

[0122] Example 2 2.1

[0124] A liquid crystal elastomer-liquid metal hollow fiber is prepared by the following method: Figure 1 As shown:

[0125] Step 1, ultrasonically clean a glass capillary with a length of 600 mm and an inner diameter of 1500 μm in ethanol and deionized water, and then dry it;

[0126] Step 2, injecting the mixed stock solution with dynamic covalent bonds into the capillary wall, wherein the content of the monomer with dynamic covalent bonds is 15%, the content of the liquid crystal monomer with monofunctional groups is 15%, the content of the liquid crystal monomer with dual monofunctionality is 40%, the content of the chain extender is 25%, the content of the crosslinker is 5%, and the content of the photoinitiator is 1%. After standing for a period of time to react, it is fixed on a high-speed motor for high-speed rotation, and the motor rotates at a speed of 1500rpm. After repeated spin coating, a layer of liquid crystal hollow film with dynamic covalent bonds with a thickness of 400μm is formed on the capillary wall;

[0127] Further, a polymerizable liquid crystal monomer stock solution with different reactive functionalities at the end is repeatedly spin-coated, wherein the content of liquid crystal monomer with a single functional group is 25%, the content of liquid crystal monomer with dual single functionality is 45%, the content of chain extender is 25%, the content of cross-linking agent is 4%, and the content of photoinitiator is 1%. After standing for a period of time to react, it is fixed on a high-speed motor for high-speed rotation, and the motor rotates at a speed of 2000rpm. After repeated spin coating, a layer of liquid crystal hollow fiber with a thickness of 500μm is formed on the capillary wall;

[0128] Step 3, immersing the glass capillary in hydrofluoric acid for etching, repeatedly washing the liquid crystal layer of the etched glass tube with clean water and drying it, and then stretching it to change it from a multi-domain state to a single domain state, stretching it to 150% of its original length, and further irradiating it with ultraviolet light to cause the second step of cross-linking, the concentration of the hydrofluoric acid used is 30%, the etching time of the glass tube is 20 minutes, the wavelength of the ultraviolet light is 365nm, and the light intensity is 200mW / cm 2 , the illumination time is 40min;

[0129] Step 4: Inject liquid metal into the hollow liquid crystal tube to form a liquid crystal / liquid metal fiber with a "skin-core structure", such as Figure 2 As shown, the gallium content in the liquid metal is 68%, the indium content is 12%, the copper content is 2%, the zinc content is 15%, the aluminum content is 1%, and the tin content is 2%; then a metal wire is connected to the end of the fiber, and polyvinyl alcohol acetal glue is used to seal both ends.

[0130] The dynamic covalent bond used in the outermost material of this embodiment is a disulfide bond-based dynamic bond, and the outermost material contains the following dynamic covalent bond monomers:

[0131]

[0132] The structural formula of the monofunctional polymerizable liquid crystal monomers in the outermost layer and the middle layer of this embodiment is as follows:

[0133]

[0134] The structural formulas of the bifunctional polymerizable liquid crystal monomers in the outermost layer and the middle layer of this embodiment are as follows:

[0135]

[0136] Furthermore, we tested the sensing performance of the liquid crystal / liquid metal fiber. In this embodiment, we prepared a liquid crystal / liquid metal fiber with a wall thickness of 500 μm, and tested the sensing signals output when the fiber was stretched, bent, and compressed. Figure 3 As shown, the experiments show that as the thickness of the fiber's liquid crystal cortex becomes thinner, the fiber's sensitivity becomes higher, and under the three force mechanisms, compressing the fiber's cross section will cause the signal change to be very obvious. 2.2

[0138] A liquid crystal elastomer artificial muscle bundle with sensing function is prepared by the following method:

[0139] Two fibers are placed side by side and closely attached together, and then the fiber bundle is heated to trigger the bond exchange of dynamic covalent bonds, which can further assemble into an artificial muscle fiber bundle. Furthermore, the heating temperature is 50° C. and the heating time is 100 min.

[0140] When different electricity is applied, the fiber bundle has different shrinkage speeds and shrinkage rates, such as Figure 4 As shown in the experiment, the contraction speed and contraction rate increase with the increase of the voltage. Furthermore, the fiber bundle is assembled on an artificial arm. When electricity is applied, the fiber bundle can contract and pull the artificial arm up. At this time, the contraction process of the fiber bundle is recorded by the sensor fiber in the fiber bundle, realizing real-time signal feedback, such as Figure 5 At the same time, the fiber bundle can be further assembled into an artificial finger. When powered on, the finger can be bent and pressure can be formed between the finger and the object. By sliding the object, the shape of the object surface can be fed back in real time, such as Figure 6 shown.

[0141] Example 3 3.1

[0143] A liquid crystal elastomer / liquid metal hollow fiber is prepared by the following method: Figure 1 As shown:

[0144] Step 1, ultrasonically clean a glass capillary with a length of 1000 mm and an inner diameter of 2000 μm in ethanol and deionized water, and then dry it;

[0145] Step 2, injecting the mixed stock solution with dynamic covalent bonds into the capillary wall, wherein the content of the monomer with dynamic covalent bonds is 15%, the content of the liquid crystal monomer with monofunctional groups is 0%, the content of the liquid crystal monomer with dual monofunctionality is 50%, the content of the chain extender is 20%, the content of the crosslinker is 14%, and the content of the photoinitiator is 1%. After standing for a period of time to react, it is fixed on a high-speed motor for high-speed rotation, and the motor rotates at a speed of 2000rpm. After repeated spin coating, a layer of liquid crystal hollow film with dynamic covalent bonds with a thickness of 800μm is formed on the capillary wall;

[0146] Further, a polymerizable liquid crystal monomer stock solution with different reactive functionalities at the end is repeatedly spin-coated, wherein the content of liquid crystal monomer with a single functional group is 40%, the content of liquid crystal monomer with dual single functionality is 35%, the content of chain extender is 15%, the content of cross-linking agent is 9%, and the content of photoinitiator is 1%. After standing for a period of time to react, it is fixed on a high-speed motor for high-speed rotation, and the motor rotates at a speed of 4000rpm. After repeated spin coating, a layer of liquid crystal hollow fiber with a thickness of 1000μm is formed on the capillary wall;

[0147] Step 3, immersing the glass capillary in hydrofluoric acid for etching, repeatedly washing the liquid crystal layer of the etched glass tube with clean water and drying it, and then stretching it to change it from a multi-domain state to a single domain state, stretching it to 150% of its original length, and further irradiating it with ultraviolet light to cause a second step of cross-linking, the concentration of the hydrofluoric acid used is 20%, the etching time of the glass tube is 30 minutes, the wavelength of the ultraviolet light used is 365nm, and the light intensity is 100mW / cm 2 , the illumination time is 50min;

[0148] Step 4: Inject liquid metal into the hollow liquid crystal tube to form a liquid crystal / liquid metal fiber with a "skin-core structure", such as Figure 2 As shown, the gallium content in the liquid metal is 58%, the indium content is 12%, the copper content is 2%, the zinc content is 10%, the aluminum content is 0%, and the tin content is 18%; then a metal wire is connected to the end of the fiber, and epoxy resin glue is used to seal the two ends.

[0149] The dynamic covalent bond used in the outermost material of this embodiment is a dynamic bond based on a boron-oxygen bond, and the outermost material contains the following dynamic covalent bond monomers:

[0150]

[0151] The structural formula of the monofunctional polymerizable liquid crystal monomers in the outermost layer and the middle layer of this embodiment is as follows:

[0152]

[0153] The structural formula of the bifunctional polymerizable liquid crystal monomers in the outermost layer and the middle layer of this embodiment is as follows:

[0154]

[0155] Furthermore, we tested the sensing performance of the liquid crystal / liquid metal fiber. In this embodiment, we prepared a liquid crystal / liquid metal fiber with a wall thickness of 1000 μm, and tested the sensing signals output when the fiber was stretched, bent, and compressed. Figure 3 As shown, the experiments show that as the thickness of the fiber's liquid crystal cortex becomes thinner, the fiber's sensitivity becomes higher, and under the three force mechanisms, compressing the fiber's cross section will cause the signal change to be very obvious. 3.2

[0157] A liquid crystal elastomer artificial muscle bundle with sensing function is prepared by the following method:

[0158] Two fibers are placed side by side and closely attached together, and then the fiber bundle is heated to trigger the bond exchange of dynamic covalent bonds, which can further assemble into an artificial muscle fiber bundle. Furthermore, the heating temperature is 50° C. and the heating time is 100 min.

[0159] When different electricity is applied, the fiber bundle has different shrinkage speeds and shrinkage rates, such as Figure 4 As shown in the experiment, the contraction speed and contraction rate increase with the increase of the voltage. Furthermore, the fiber bundle is assembled on an artificial arm. When electricity is applied, the fiber bundle can contract and pull the artificial arm up. At this time, the contraction process of the fiber bundle is recorded by the sensor fiber in the fiber bundle, realizing real-time signal feedback, such as Figure 5 At the same time, the fiber bundle can be further assembled into an artificial finger. When powered on, the finger can be bent and pressure can be formed between the finger and the object. By sliding the object, the shape of the object surface can be fed back in real time, such as Figure 6 shown.

[0160] The above is only a preferred embodiment of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A liquid crystal elastomer-liquid metal hollow fiber, characterized in that: The liquid crystal elastomer-liquid metal hollow fiber is a bundle fiber structure with a three-layer core. The material of the outermost layer is a liquid crystal elastomer with dynamic covalent bonds, which can undergo dynamic bond exchange under external stimulation. The material of the middle layer is a thermally responsive liquid crystal elastomer, which undergoes a phase transition when heated, thereby causing macroscopic shrinkage deformation. The core layer material is a flowing liquid metal with electrical conductivity and electrothermal properties.

2. The liquid crystal elastomer-liquid metal hollow fiber according to claim 1, characterized in that: The thickness of the outermost layer ranges from 3 μm to 1000 μm, the thickness of the middle layer ranges from 3 μm to 1000 μm, the diameter of the core layer material ranges from 2 μm to 1200 μm, and the length of the bundled fibers ranges from 15 mm to 1500 mm.

3. The liquid crystal elastomer-liquid metal hollow fiber according to claim 1, characterized in that: The dynamic covalent bond is an ester-based dynamic bond, a disulfide-based dynamic bond, a boron-oxygen-based dynamic bond, a silicon-ester-based dynamic bond, a diselenide-based dynamic bond, or a nitrogen-containing functional group-based dynamic bond; The liquid crystal monomer with a single functional group used in the material of the outermost layer is one or more of the following: The dual monofunctional liquid crystal monomers used in the outermost layer of the material are one or more of the following: The liquid crystal used in the material of the intermediate layer is a polymerizable liquid crystal monomer with different reactive functionalities at the end, and the liquid crystal phase transition temperature of the liquid crystal monomer is 25° C. to 180° C. Preferably, the liquid crystal monomer is a single liquid crystal monomer or a mixture of two or more liquid crystal monomers. More preferably, the monofunctional liquid crystal monomer is one or more of the following: The dual monofunctional liquid crystal monomer is one or more of the following:

4. The liquid crystal elastomer-liquid metal hollow fiber according to claim 1, characterized in that: The liquid metal consists of the following components and mass percentages: 52-78% gallium, 5-12% indium, 0.5-2% copper, 7-20% zinc, 0-1.2% aluminum, and 0-18% tin.

5. The method for preparing the liquid crystal elastomer-liquid metal hollow fiber according to claim 1, characterized in that: The following steps are involved: Step 1, cleaning the tubular mold and then drying it; Step 2, injecting the mixed stock solution with dynamic covalent bonds into the mold, standing for a period of time to react, fixing it on a high-speed motor for high-speed rotation, the motor rotation speed is 500-5000rpm, forming a layer of liquid crystal hollow film with dynamic covalent bonds on the inner wall of the mold, preferably, in order to increase the thickness of the liquid crystal hollow film, it can be repeatedly spin-coated; further using a polymerizable liquid crystal monomer stock solution with different reaction functionalities at the end for spin coating, standing for a period of time to react, forming a hollow cortical structure with an outer layer of a liquid crystal elastomer layer with dynamic covalent bonds and a middle layer of a thermally responsive liquid crystal elastomer layer; Step 3, immersing the mold treated in step 2 in hydrofluoric acid for etching, repeatedly washing the liquid crystal layer of the mold with clean water, drying it, and then stretching it to change it from a multi-domain state to a single-domain state, stretching it to 150% to 200% of its original length, and further irradiating it with ultraviolet light to cross-link the carbon-carbon double bonds inside the fiber to obtain a hollow liquid crystal hollow tube with an outermost layer and an intermediate layer; Step 4: injecting liquid metal into the hollow liquid crystal hollow tube to form the liquid crystal elastomer-liquid metal hollow fiber.

6. The preparation method according to claim 5, characterized in that: In step 4, glue is used to seal both ends, and the ends are connected to metal wires. Preferably, the viscosity of the glue ranges from 300 to 10,000 cps, and the glue is modified acrylic adhesive, epoxy resin glue, polyvinyl acetal glue, α-ethyl cyanoacrylate, etc.

7. The preparation method according to claim 5, characterized in that: In step 1, the mold is a glass capillary, which is ultrasonically cleaned in ethanol and deionized water. Preferably, the length of the glass capillary is in the range of 10 mm to 1000 mm, and the diameter of the inner wall of the glass tube is in the range of 10 μm to 2000 μm.

8. The preparation method according to claim 5, characterized in that: In the step 2, the mixed stock solution with dynamic covalent bonds includes dynamic covalent bond monomers, liquid crystal monomers with monofunctional groups, liquid crystal monomers with dual monofunctionality, chain extenders, crosslinkers and photoinitiators, wherein the content of the dynamic covalent bond monomers is 5% to 25%, the content of the liquid crystal monomers with monofunctional groups is 0% to 40%, the content of the liquid crystal monomers with dual monofunctionality is 50% to 90%, the content of the chain extender is 20% to 40%, the content of the crosslinker is 30% to 50%, and the content of the photoinitiator is 0.5% to 2%; The polymerizable liquid crystal monomer stock solution with different reactive functionalities at the ends includes a liquid crystal monomer with a monofunctional group, a liquid crystal monomer with dual monofunctionality, a chain extender, a crosslinking agent and a photoinitiator, wherein the content of the polymerizable liquid crystal monomer with a monofunctionality is 0% to 45%, the content of the polymerizable liquid crystal monomer with dual reactive functionality is 60% to 95%, the content of the chain extender is 15% to 45%, the content of the crosslinking agent is 25% to 55%, and the content of the photoinitiator is 0.5% to 2%.

9. The preparation method according to claim 5, characterized in that: The concentration of hydrofluoric acid used in step 3 is 5% to 40%, the etching time is 10 min to 50 min, the wavelength of the ultraviolet lamp used is 365 nm, and the light intensity is 10 to 300 mW / cm 2 , the illumination time is 2 to 30 minutes.

10. The use of the liquid crystal elastomer-liquid metal hollow fiber as described in claim 1 in an artificial muscle bundle, wherein the artificial muscle bundle is formed by two or more of the liquid crystal elastomer-liquid metal hollow fibers through dynamic covalent bond exchange on the surface of the fiber bundle, and preferably, two or more of the liquid crystal elastomer-liquid metal hollow fibers are placed side by side and tightly fitted together, and then bonded together by heating, the heating temperature is 40 to 100°C, and the heating time is 10 min to 100 min.

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